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A number of crucial aircraft programs from both incumbent and start-up manufacturers will mark initial events in the new year with new aircraft that will shape the future of air transport for decades.
Following the entry of the Airbus A320neo family in 2016, Boeing is introducing the latest version of its narrowbody, the 737 MAX. From a pure volume point of view, the MAX will be the most important new model that will start revenue flying. But there are other firsts, too. The A321neo will ...

However, to bounce back off the comments, "The 787-10 will roll out and fly for the first time in 2017. It will be the most fuel-efficient widebody airliner ever built. And it is likely to retain that title for years to come.", ...... one can bet that ;

-- Boeing would agree ;
-- Rolls-Royce would probably like to add something like, "Indeed, especially the versions powered by RR Trent-1000 TEN engines" ;
-- Airbus would be quick to contradict, with John LEAHY arguing that, "The A350-XWB-900 will stake that claim, and prove it for far more years than Boeing would even dare to imagine", ..... and ....
-- GE would agree with Boeing, and try to outgun RR by arguing, "An up-graded GEnx-1B PIP 2 will be the better engine choice".

"You pays your money, and you takes your choice" !

But professional Aviation Specialists are at their best when they avoid going in for odious comparisons, & / or championing some product or other in sales-promotion style, huffing & puffing !

The 787-10 looks like the unchallenged leader in fuel efficiency for widebody airliners.
The 787-10 carries 330 pax with an MTOW of 254 tonnes and engines of 76,000 lb thrust.
The A350-900 carries 315/325 pax with an MTOW of 280 tonnes and engines of 84,000 lb thrust.
No contest.
Of course the A350-900 has other fine qualities, such as longer range than the 787-10.

Thanks.
Yes, the 76,000 lbs thrust (extensible without penalty, allegedly, to 78,000 lbs if needed) applies to the RR Trent 1000 power-plants (TEN or not TEN).

Sadly, there can be "no contest" till the B787-10 actually flies in operations. We shall have to await actual, comparative results. We're not there yet.

The interesting thing claimed about the A350-XWB-900 is its flexibility (notably in its "regional" version", as well as in its standard, LR, & ULR versions). But there, too, we shall have to wait till 2018 or 2019 for full concrete data and possible comparisons.

The RR T-XWB-84 engine has just confirmed, in operations, (and over many flight hours & flight cycles, not merely the first 3,000 hours) an increase in fuel-burn efficiency beyond expectations of between 1% & 2%, with some saying, rightly or wrongly, that this will stabilise at around 1.6%.

Experience tends to show that it is best to give a wide-berth to "paper statistics", and to wait for hard, concrete data, capable of offering "apples-to-apples" comparisons.

Of course, RR will be in the good seat for delivering the facts & the stats on both aircraft ! Arguably more objective than Boeing or Airbus.
We are in for interesting times.